This invention relates to mechanical grape harvesters. The removal of fruit from the area of the head of the vine and the cordon wire area (at the centerline of the row) is one of the most difficult tasks in machine harvesting. All of the foliage and growth of the vine must be penetrated to achieve this. In the area of the head of the vine (the normally relatively massive area at the top of the trunk from which the fruit-bearing canes originate) removal of cane pruned grapes is especially difficult. Wood growth of 6 to 8 inches on either side of the row center is not unusual. Some vineyards have massive growth to an overall width of 20 to 30 inches, which precludes machine harvesting without cutting back the wood beforehand.
A very large number of the more popular wine grape varietals have a very large percentage of grape production in the area immediately adjacent the vine head and the cordon wire. This can result in 60-80percent of the crop being within 4 to 6 inches of the row centerline, with 20-30percent along the center. In order to achieve a high percentage of fruit removal it is necessary to have very good coverage of the area immediately adjacent the row centerline and the vine head.
Another characteristic of the majority of wine grapes is the extreme difficulty or impossibility of removal of fruit in the vine head and cordon wire area by shaking. The grapes are simply too entwined and can only be removed completely by direct contact.
A satisfactory harvesting of the fruit in the vine head or cordon area is therefore dependent on complete penetration of the rod into this area in an even and consistent manner. In order to avoid damage to the vine structure and to avoid excessive leaf removal, a minimum disturbance of this area is necessary.
The type of mechanical grape harvester is most widespread use is the striker rod machine, as exemplified in Horn U.S. Pat. No 3,688,482, issued on Sept. 5, 1972. Such machines have a plurality of oscillating vertical shafts, each shaft having a plurality of generally horizontal, elongated straight striker rods, each mounted at one end to the shaft for oscillation thereby. As the harvester moves along a row of fruit-bearing vines, the oscillation of the shafts causes the striker rods to swing repeatedly into and out of striking engagement with the fruit of the vines so as to dislodge the fruit from the vines.
Whether the straight striker rods shown in the Horn patent have been mounted as shown in either FIG. 3 or FIG. 4 thereof, it has been necessary to orient the rods at a relatively small angle -- typically as shown in FIG. 2 of the Horn patent -- to the centerline of the vine row.
Extensive harvesting experience has proven that, as compared to the previously conventional form of mounting shown in Horn FIG. 3, the resilient striker rod mounting of Horn FIG. 4 significantly reduces flexure strain and fatigue failure at the mounting end and reduces damage to the vines and posts struck by the striker rods. The use of the thin metal sleeves on the free end of the rods has also reduced splintering of the rod. However, such experience has also shown that the Horn striker rods have not been fully satisfactory in harvesting efficiency, for the reasons set forth in more detail below. Nor has experience been satisfactory with oscillating paddles or panels, similarly oriented to the vine, with or without the inwardly projecting hooks or other members, as for example disclosed in U.S. Pat. No. 3,439,482, issued on April 22, 1969 to Orton.
Such picking devices, and their narrow-angle orientation of the strikers to the centerline of the vine, have a number of serious faults:
a. In order to achieve the necessary penetration of the rod ends into the vines, a substantial length of the rod will strike sidewardly against the foliage of the vine and dislodge many leaves while striking and removing the grapes. These leaves then mix with the harvested fruit on the conveyors of the harvesting machine. Although most of these leaves can be removed with blowers, the juice entrapped on the leaves will be lost.
b. Inwardly projecting hooks or other members fastened to the striker rods, paddles or panels in an attempt to provide better vine penetration will rake the vine, macerating the fruit and removing and fragmenting excessive leaves. The faster the ground speed of the harvester -- for maximum harvester production -- the more deleterious is this raking action.
c. The ends of the straight rods or paddles cut canes, leaves and fruit, causing vine damage, lowered fruit quality, and juice loss.
d. Because of the narrow angle of the rod or paddle to the centerline of the vine, it is difficult for the rod or paddle end to penetrate the head of the vine (the region at the top of the vine trunk where the canes, arms or cordons branch out). As a consequence, fruit removal from the head of the vine is incomplete and a harvest loss is incurred. This is particularly so with tough-stemmed varietals of grapes.
e. Because of the cushioning effect of the vine growth a very rapid oscillation of the rods has been necessary for the rods to penetrate the vines and impact against the grapes with sufficient force to remove the grapes. This has been particularly so for the harvesting of tough-stemmed grape varietals. Frequencies of 400 to 450 cycles per minute, resulting in impacts every 11/2 to 2 inches along the vine, are commonly used. The attendant high rod tip speeds and repetitive striking of the vine results in damage to the vine and leaf removal which is undesired but unavoidable if the variety is to be harvested.
With a significant number of tough-stemmed varietals (e.g., Ugni Blanc, Zinfandel and Emerald Riesling), the problem is compounded by the thin-skinned, easily damaged character of the grape. Other varietals, such as Carrignan, have extremely brittle wood which is very susceptible to cane damage. These varietals have generally been considered as unsuitable for machine harvesting.
f. On most vinifera grapevines the fruit is too tough-stemmed to be removed by shaking the vine. Removal will only occur if the vines are penetrated and the fruit is struck. With multiple, narrow-angle rods on each side of the vine and with the conventional narrowly spaced oscillatory shafts on which these rods are mounted, an occasional bushy vine is so embraced by the rods that it will oscillate side-to-side in synchronism with the rod action and the rods do not penetrate the vine to strike and remove the fruit therefrom.
Such vine oscillation has also been observed in the harvesting of varieties such as Thompson Seedless having a relatively high yield and pendulous, free-hanging clusters. The vine oscillation has occurred at random intervals for distances of 40 to 50 feet in some fields. Thompson Seedless yields 60 to 80 pounds of fruit per vine and with a 10-foot spacing a loss of picking effectiveness in 40 to 50 feet of a row can result in a loss of 300 to 400 pounds of fruit for each occurrence.
g. Wide crossarm trellises are often used for foliage support to shade the fruit underneath from sunburn. Such trellises cannot be straddled by a harvester machine having the conventional narrow spacing between the opposed oscillating strike arm shafts.
Attempts have been made to overcome some of these problems by moving the oscillating shafts further apart, thereby increasing the angle of the rods or paddles to the centerline of the machine. These attempts have generally been unsatisfactory. As the oscillating rods are moved along the row by the harvesting machine the tips of the rods will penetrate and strike the vine at one point along its length. The rods will then be removed from the vine to penetrate the vine again, on the next cycle of oscillation at another point along the vine. With the same ground speed and same oscillation frequency, more of the vine will be skipped with a greater rod inclination and the amount of grapes left unharvested will increase. The amount of skipping can be reduced by reducing the ground speed of the harvester while using the same oscillation frequency. This, however, reduces the rate of harvesting production correspondingly. The amount of skipping can also be reduced without a reduction in ground speed by increasing the oscillation frequency. This too is disadvantageous since the kinetic energy of the striker rods varies as the square of their speed and even a small increase in speed of oscillatory movement beyond that necessary to pick the fruit will result in substantial damage to the vines and fruit and to the striker rods. Then again, the ground speed can be reduced and the oscillation frequency increased to reduce the degree of skipping. This too is disadvantageous since the rate of harvest production will go down while the amount of damage increases.
It is the principal object of this invention to overcome the above-enumerated faults of present harvesting machines and provide a machine capable of successful harvesting on a commercial scale with widely spaced oscillating striker rod shafts and a large angle between the striker rods and the longitudinal centerline of the machine.
It is a further object of this invention to provide such a machine in which the ground speed can be increased and/or the oscillation frequency reduced, as compared to conventional machines, without a corresponding loss in picking efficiency.